@Jovychris_A -

Thank you, thank you, thank you for your help and very clear instructions!

I followed them with success until I got to this step: "In the Pay Taxes & Other Liabilities window, check the tax or other liability you want to pay from the list. 

When I went to check the correct tax/liability to pay (under the Pay Liabilities tab), it was not listed.

Luckily, I was able to work out how to fix this on my own by going back into the original check that I had been instructed to modify (by listing the amount -$3693 under the "Expenses'' tab) and instead, listed the -$3693 under the Payroll Liabilities tab (I've attached a new screenshot showing an example of what I did, just in case anyone else ever has the misfortune encountering this issue).

After this, the "AZ Withholding" tax liability for that quarter reappeared under the Pay Liabilities tab with the correct remaining $3693 amount due and I was able to follow the rest of your instructions to select and mark it as paid.  :)

I believe I can finally mark this issue as resolve.  Thank you all for your time and advice!